In drilling through subterranean formations, the borehole, either accidently or by design, frequently is not straight. In drilling wells, for instance, the borehole will sometimes assume a curved path, and in other cases a deviated borehole is intentionally drilled. In drilling generally horizontal boreholes into mineral formations, the initial part of the borehole often is intentionally caused to assume a curved path.
In some cases, removal of drillpipe, tubing or casing from a curved borehole is difficult because tension applied to the conduit causes it to bind against the inside of the curved portion of the borehole. This problem often results in lost production time and/or repair, and in some cases stuck pipe results in loss of use of the borehole.
Prior to this invention, there was no satisfactory way to remove pipe from a curved borehole if the common prior art method of removing pipe by pulling from the surface end of the pipe was not successful.